1. Field
The present invention relates to filters for fluids such as hydraulic oil, transformer oil and lubricating oil, and more particularly to a fluid collector for use therewith.
2. Description of the Prior Art
Fluid filters for removing dirt, common residue, abrasive particles, acid condensate, sludge and corrosive matter from fluids such as engine lubricating oil are well known in the art. These filters are usually packaged either as disposable canisters, replaceable cartridges, or as containers for containing generally one or more filter elements which are formed with wound layers of tissue. Inflow and outflow connections are provided at the container inlet and outlet ports. Fluid entering the container will flow freely to an end of each filter element where it enters the filter element. The fluid then flows axially through each filter element in the interstices between the layers of filter tissue so that the dirt and sludge is removed from the fluid by the tissue layers. When the filter contains only one filter element, the fluid flows from one end of the container to the other, through one end of the filter element, then out the other end of the filter element. The fluid then is directed by a fluid collector to a centrally located flow path which is connected to the outlet port.
When two filter elements are used, the fluid flows from both ends of the container through the filter elements to a collector located between the filer elements. The collector has a passageway which directs the fluid to the centrally located flow path, where it is directed out the outlet port. When four filter elements are used in the filter container, the filter acts in a similar manner as would two filters having dual filter elements. The filter elements are organized into two pairs of opposed filter elements so that the fluid flows from both ends of each pair through the filter elements to the collector which is located between the two opposed filter elements of each pair. Therefore, a container having four filter elements typically has two fluid collectors.
The pressure drop across the entire filter may be from fifteen pounds per square inch (P.S.I.) to ninety P.S.I. or more, resulting in substantial compressive forces being exerted hydraulically on the tissue layers. These forces tend to compress and distort the filter elements, particularly at the end of each filter element where filtered fluid exits. Fluid collectors have been utilized to receive the filtered fluid from the filter elements and to transport that fluid through one or more passageways in the collector to the centrally located flow path. As disclosed in U.S. Pat. No. 4,017,400 to Schade, these collectors generally have an annular portion which extends into the adjacent filter element ends to form a seal which separates the filtered from unfiltered fluid. Usually a screen is disposed between the collector and filter element to hold the filter element end in spaced relation to the collector so that filtered fluid is free to flow from the filter element end into the collector.
It has been found that the pressure forces which tend to compress and distort theffilter elements also tend to force the layers of tissue of the filter element to be pressed down into the holes in the screen, thereby decreasing the flow of filtered fluid into the collector. This is particularly a problem in industrial applications where relatively high flowages through the filter elements are required.